Rigless well completion method

ABSTRACT

A method and system for completing a well below the bottom of a body of water includes assembling a completion string at a location away from a location of the wellbore, moving the assembled completion string to the location of the wellbore and inserting the assembled completion string into the wellbore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to and the benefit ofProvisional Patent Application Ser. No. 61/045,981 filed Apr. 18, 2008.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of completion of wellboreconstruction by insertion into a drilled well of a production pipe. Morespecifically the invention relates to methods and devices for completingor re-completing wellbores below the bottom of a body of water.

2. Background Art

Wellbore completion is the process of inserting one or more “strings” ofpipe or conduit into a wellbore that has been drilled. The conduit maybe a so-called “casing”, which is typically cemented into the wellboreafter drilling is completed, or the conduit may be a “production tubing”which is inserted into a wellbore that already has a casing. Theproduction tubing may include a number of different devices, such asflow control valves, sensors, control lines, artificial lift devices(e.g., gas lift valves) and annular sealing devices known as packers toseal the annular space between the casing and the outside of theproduction tubing.

When a wellbore is drilled, a lifting device known as a “drilling rig”is used. Operations performed in the wellbore from the drilling riginclude moving drill pipe into and out of the wellbore, and running andcementing the casing in place. Such operations include threadedlycoupling segments (“joints” or “stands”) of the particular pipe end toend, and moving the assembled pipe segments along the wellbore by usinglifting equipment on the drilling rig.

Drilling rigs are known for use in drilling through formations below thebottom of a body of water. Certain types of such a drilling rigs floaton the top of the water and lower pipe and devices through a “riser”that connects a wellhead proximate the sea floor to the floatingdrilling platform. See, for example, U.S. Pat. No. 6,415,867 issued toDeul et al. for a general description of drilling procedures from afloating drilling structure.

Once a wellbore has had casing cemented in place, because the casingmaintains the mechanical integrity of the wellbore, the continuedpresence of a floating drilling structure such as a drilling rig isunnecessary

The cost of operating a floating drilling structure can be extremelyexpensive and includes functionality unnecessary for the wellborecompletion process. Further, in some circumstances, drilling rigs couldbe more advantageously used elsewhere for such activities as drillingoperations.

SUMMARY OF THE INVENTION

A method for completing a well below the bottom of a body of wateraccording to one aspect of the invention includes assembling acompletion string at a location away from a location of the wellbore.The assembled completion string is moved to the location of thewellbore. The assembled completion string is then inserted into thewellbore. Also the well completion can be removed from a well for repairor replacement, using the same method as described herein.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic depiction of a method for completing a well orretrieving a well completion using a pre-assembled completion accordingto one example of the present invention.

FIG. 1A shows a schematic description of a safety and guiding assemblyaccording to one example of the present invention.

FIG. 2 shows a schematic depiction of a method for running thecompletion through a wellhead and a safety and guiding assemblyaccording to one example of the present invention.

FIG. 3 shows a schematic depiction of a safety and guiding assemblysystem installed on a subsea wellhead, according to one example of thepresent invention.

DETAILED DESCRIPTION

In a method according to the invention, a well completion “string”, suchas a production tubing string formed from threadedly coupled pipesections (i.e., “joints” or “stands”), may be preassembled at a shorebase or other facility away from a wellsite. The wellsite is typicallybelow the bottom of a body of water and would be drilled using afloating drilling structure. See, e.g., U.S. Pat. No. 6,415,867 issuedto Deul et al. for a general description of drilling procedures from afloating drilling structure.

The techniques used to assemble the completion string may be similar tothose used to preassemble product transportation pipeline, except thatthe pipe joints or stands in production tubing may be threadedly coupledrather than welded. Typically, the completion string would be assembledlying substantially horizontally, with an end being towed out into thewater by a deployment vessel. Alternatively, the completion string canbe assembled by a vessel where the string is suspended in the sea fromsuch vessel. The assembled completion string can be pressure tested,function tested and inspected prior to being towed out to the wellsite.The present method of assembling and testing will remove the timerequired for such assembly from being performed on a drilling rig orsimilar floating vessel.

As an example of possible cost savings using a method according to theinvention, one fiber optic splice in a completion string having fiberoptic communication capabilities can typically take 6 to 8 hours of rigtime, at a daily cost (2008) of up to one million US dollars. Theproposed method significantly reduces this expenditure, and allows formore detailed and extended testing of the assembled completion systemprior to deployment. As the string assembly is finished, a supportvessel may suspend the other end of the completion string for deploymentto the wellsite. The well completion string may be fully or partiallyfilled with air or other gas to create the buoyancy required for safetransportation under the sea surface to the wellsite. In an alternativeexample, external floatation devices may be used in addition to air orgas filling for buoyancy, including both active and passive flotationaids such as foam modules or air cans. Using external buoyancy devicesmay be necessary when remotely assembling so called “sand-face”completion sections. Such sections typically contain sand screens, whichbeing permeable, would make internal air filling of the assembledcompletion string impossible. The upper portions of the completionstring longitudinally displaced from the screen or screens could,however, be sealed with an internal sealing device or plug, and use theinternal air buoyancy methodology described above

Prior to installing an assembled completion string into the wellbore,the wellbore should be in a “safe” status by using downhole barrierssuch as casing plugs being installed, or by not yet being perforated(wherein explosive charges are used to penetrate the wellbore casing,cement external to the casing and some of the productive formationoutside the wellbore). For pulling completion strings already disposedin wellbores out from such wellbores, using the above described methods,the wellbore should first be safely secured to prevent fluid entry intothe wellbore from formations into which perforations extend, or in whichscreens are disposed. Securing a previously completed wellbore may beperformed, for example using well known fluid pressure barriers, forexample, mechanical plugs. In other examples high density fluids (“killfluid”) may be pumped into the wellbore, or remotely operated downholevalves or similar maybe used. See, for example, U.S. Pat. No. 5,343,955issued to Williams or U.S. Pat. No. 5,167,284 issued to Leismer for adescription of typical wellbore safety valves.

The deployment vessel and support vessel may then move to the wellsiteto enable installing the completion string. Referring to FIG. 1, thedeployment vessel 20 may suspend a wellbore connection end 32 of a wellcompletion string 30. Wellbore connection end 32 is end of wellcompletion string 30 that will be connected to wellbore 10. Wellbore 10may be disposed beneath subsurface wellhead 14, shown in the inset FIG.1A in FIG. 1, disposed on the water bottom. Placement end 34 ofcompletion string 30 may be disposed directly above wellhead 14, andplacement end 34 lowered into the water from support vessel 50, such asby a winch or similar device. Deployment vessel 20 may move towardwellhead 14 as placement end 34 of completion string 30 is lowered.Deployment vessel 20 may use remotely operated vehicle (“ROV”) 60 oftypes well known in the art to deploy tools (not shown) and video camera(62) to cause completion string 30 to move through a suitable opening inthe top of wellhead 14 (shown in greater detail in FIGS. 2 and 3). ROV60 is typically connected to deployment vessel 20 through ROV umbilical64, by which power may supplied to ROV 60 and data, typically includingvideo, may be delivered to deployment vessel 20. ROV 60 may also deployelectrical and/or hydraulic cables to connect control equipment on thedeployment vessel 20 to suitable controlled devices on the wellhead 14,such as blowout preventers (“BOPs”).

Tubulars, even large size tubulars such as, for example 7 inch diametertubulars, can bend when long in comparison to the diameter. This bendingis a natural property of the materials used to make completion string30, and it is necessary for being able to run and install tubular intodeviated wellbores, for example. This natural bending will allow anentire well completion string towed out to the wellhead location to bendin the water. What may be observed in FIG. 1 is that completion string30 is bent from a horizontal orientation to a vertical orientationthrough wellhead 14 and into wellbore 10. The lowering of completionstring 30 into wellbore 10 continues with deployment vessel 20 movingtoward wellhead 14, while lowering completion string 30 into wellbore10. Air can be pumped into or evacuated from within completion string 30by deployment vessel 20 to create any positive or negative buoyancyrequired for placement of completion string 30 into wellbore 10.Alternatively, or additionally, external air canisters may be used toprovide buoyancy. Such air canisters may be released from the completionstring, for example, by using the ROV 60 or by acoustic command from thedeployment vessel 20 or support vessel 50. It may be desirable fordeployment vessel 20 to approach wellbore 10 from the same direction asthe main ocean currents in the area of wellbore 10, as shown in FIG. 1.Such an approach may assist in the deployment of well completion string30 by allowing the main ocean currents to push or guide well completionstring 30 to its desired location.

In some examples of the present invention, support vessel 50 may assistin the deployment of well completion string 30. Support vessel 50 mayperform such as operations as assisting in the placement of wellcompletion string 30 or securing sections of well completion string 30while other sections are being connected to wellhead 14.

FIG. 1 further depicts control umbilical 70. Control umbilical 70 andwellhead control umbilical 74 are connected through umbilical connector72. These elements and their purpose are more fully described below.

FIG. 2 shows well completion string 30 as it is being moved throughwellhead 14. At the time of assembly, well completion string 30 may becharged with air for buoyancy. As well completion string 30 is deployedinto wellbore 10, the air inside well completion string 30 can begradually released to cause well completion string 30 to move downwardlyunder gravity, to balance the weight of well completion string 30 and toprovide added safety and deployment speed. However, well completionstring 30 is at normally connected to deployment vessel 20 by wireand/or umbilical 36, where safe deployment speeds are controlled by thespeed of deployment vessel 20 moving toward the location above wellhead14 as well as by the lowering speed of well completion string 30 bydeployment vessel (20)'s winch system.

The safety of the well completion string 30 deployment and retrieval ofthereof with respect to possible dropping of the string 30 in the watercan be addressed by having completion string filled with air asexplained above, by the deployment wire or rope from the deploymentvessel 20, and by providing external buoyancy tanks which can beactivated by, for example, sensing water pressure and/or acceleration ofthe completion string 30 through water.

When well completion string 30 has been “landed” that is, fully insertedinto wellbore 10 and a “tubing hanger” (not shown) is seated in wellhead14, equipment disposed on deployment vessel 20 may be used inconjunction with control umbilical 70 shown in FIG. 1 to set packer(s),tubing hangers, and similar equipment, as well as to pressure test thewellbore system (the casing, wellhead and completion string).Thereafter, downhole barriers such as safety plugs or valves may beopened. If the well casing was not perforated prior to completion string30 installation, such perforation can be performed when the system hasbeen pressure tested and qualified. If a so-called horizontal wellheadis used, wellhead 14 would most often be installed on the seafloor priorto installation of well completion string 30. And if a so-calledvertical wellhead is used, wellhead 14 would most often be installedafter well completion string 30 is installed. Such wellhead installationcan be performed using one or two vessels instead of a floating drillingstructure.

One example of a safety- and guiding assembly 100 to be mounted onto thewellhead guide base or a horizontal type wellhead usable with thepresent method is shown in FIGS. 2 and 3. The components may be similarto those used in conventional sea floor well completions where afloating drilling structure is used.

As shown in FIGS. 2 and 3, wellhead 14 is connected to BOP 200. Theconstruction of BOP 150 and its connection to wellhead 14 are generallyunderstood by those of skill in the art. Mechanically connected to BOP200 is lower guide funnel 110. Lower guide funnel 110 is adapted toguide well completion string 30 to properly mate with and pass throughBOP 200 into wellhead 14. While lower guide funnel 110 is shown in FIGS.2 and 3 to be conical, this shape is non-limiting.

Connectors 120 serve to mechanically connect BOP 200 to safety- andguiding assembly 100. Safety- and guiding assembly 100 typicallyconsists of two primary parts, cylindrical body 130 and upper guidefunnel 150. Upper guide funnel 150 is adapted to receive well completionstring 30 as it is lowered from deployment vessel 20 and allow wellcompletion string 30 to pass into cylindrical body 130. While upperguide funnel 150 is shown in FIGS. 2 and 3 to be conical, this shape isnon-limiting. Cylindrical body 130 serves to guide well completionstring 30 to lower guide funnel 110 as well completion string 30 islowered from deployment vessel 20.

Safety- and guiding assembly 100 may also include one or more buoyancytanks 140. Buoyancy tanks 140 are typically used to assist in placementof safety- and guiding assembly 100. Safety- and guiding assembly mayalso include dropped pipe grabber 160. Dropped pipe grabber 160 assistsin the protection of BOP 200 and wellhead 14 from accidentalmisplacement of well completion string 30 or falling objects such aspiping or tools.

Placement by deployment vessel 20 of well completion string 30 may beassisted through the use of camera 170. Camera 170 is focused on upperguide funnel 150. Camera 170 transmits data, such as video, todeployment vessel 20, typically through control umbilical 70. Such videoallows the operator of deployment vessel 20 to more closely view theplacement of well completion string 30 into upper guide funnel 150.Camera 170 is often mounted on movable arm 180; movable arm 180 isadapted to allow the operator of deployment vessel 20 to orient camera170 during placement of well completion string 30.

The operation shown in FIG. 1 may be reversed to effect repairs on thetubing string of well completion string 30. In such repair operations,the tubing string may be moved to a location away from the location ofwellbore 14, and at least one repair operation may be performed, forexample, welding, replacement of a valve or other control, replacementof a packer, etc.

Methods according to the invention may save the cost of using a floatingdrilling structure for well completions and well re-completions.

While the invention has been described with respect to a limited numberof examples, those skilled in the art, having benefit of thisdisclosure, will appreciate that other examples can be devised which donot depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A method for completing and re-completing a well below the bottom ofa body of water, comprising: assembling a well completion string at alocation away from a location of the wellbore to form an assembled wellcompletion string; moving the assembled well completion string to thelocation of the wellbore; and inserting the assembled well completionstring into the wellbore.
 2. The method of claim 1 wherein theassembling is performed substantially horizontally.
 3. The method ofclaim 2 wherein the moving is performed by suspending in the water theassembled well completion string from at least one vessel.
 4. The methodof claim 1 wherein the assembling is performed by moving one end of thewell completion string into the body of water by towing from a vesselwhile segments of the well completion string are coupled to the otherend of the string.
 5. The method of claim 1 wherein the moving comprisessuspending the assembled well completion string from a vessel disposedproximate each end of the well completion string.
 6. The method of claim1 wherein a well completion string is removed from a well and then fullyor partially disassembled horizontally at a location away from thewellbore
 7. The method of claim 1 wherein the well completion string isa drill-string.
 8. A method for wellbore intervention, comprising:lifting a pipe string from within a wellbore wherein the wellbore issituated by winching one end of the pipe string thereof toward a firstvessel on the surface of the water; moving the vessel away from alocation of the wellbore; lifting the other end of the pipe stringtoward the surface of the water by winching the other end toward asecond vessel on the surface of the water; and moving the first and thesecond vessels away from the location of the wellbore.
 9. The method ofclaim 8 further comprising moving the pipe string to a location awayfrom the location of the wellbore and performing at least one repairoperation on the pipe string.
 10. A safety and guiding assemblycomprising: a substantially cylindrical body having a proximate end, adistal end, and an outer circumference; an upper guide funnel, the upperguide funnel mechanically connected to the proximate end of thesubstantially cylindrical body and adapted to receive a well completionassembly; and a connector, the connector mechanically connected to thedistal end of the substantially cylindrical body and adapted to fastenthe substantially cylindrical body to a BOP.
 11. The assembly of claim10 further comprising a buoyancy tank, the buoyancy tank secured to theouter circumference of the substantially cylindrical body.
 12. Theassembly of claim 10 further comprising a pipe grabber, the pipe grabberdisposed on the outer circumference of the substantially cylindricalbody.
 13. The assembly of claim 10 further comprising a controlumbilical, the control umbilical in mechanical connection with thesubstantially cylindrical body.
 14. The assembly of claim 13 furthercomprising a camera, the camera in electrical connection with thecontrol umbilical.
 15. The assembly of claim 14 further comprising amovable arm, the arm in mechanical connection with the camera and inmechanical connection with the substantially cylindrical body.